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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, cl@linux.com, linmiaohe@huawei.com,
	linux-mm@kvack.org, louhongxiang@huawei.com,
	mm-commits@vger.kernel.org, torvalds@linux-foundation.org,
	willy@infradead.org
Subject: [patch 09/40] mm/migrate: avoid possible unnecessary process right check in kernel_move_pages()
Date: Sat, 17 Oct 2020 16:14:03 -0700
Message-ID: <20201017231403.WBGUY4nLK%akpm@linux-foundation.org> (raw)
In-Reply-To: <20201017161314.88890b87fae7446ccc13c902@linux-foundation.org>

From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/migrate: avoid possible unnecessary process right check in kernel_move_pages()

There is no need to check if this process has the right to modify the
specified process when they are same.  And we could also skip the security
hook call if a process is modifying its own pages.  Add helper function to
handle these.

Link: https://lkml.kernel.org/r/20200819083331.19012-1-linmiaohe@huawei.com
Signed-off-by: Hongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Cc: Christopher Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate.c |   71 +++++++++++++++++++++++++++++--------------------
 1 file changed, 43 insertions(+), 28 deletions(-)

--- a/mm/migrate.c~mm-migrate-avoid-possible-unnecessary-process-right-check-in-kernel_move_pages
+++ a/mm/migrate.c
@@ -1864,33 +1864,27 @@ static int do_pages_stat(struct mm_struc
 	return nr_pages ? -EFAULT : 0;
 }
 
-/*
- * Move a list of pages in the address space of the currently executing
- * process.
- */
-static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
-			     const void __user * __user *pages,
-			     const int __user *nodes,
-			     int __user *status, int flags)
+static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
 {
 	struct task_struct *task;
 	struct mm_struct *mm;
-	int err;
-	nodemask_t task_nodes;
-
-	/* Check flags */
-	if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
-		return -EINVAL;
 
-	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
-		return -EPERM;
+	/*
+	 * There is no need to check if current process has the right to modify
+	 * the specified process when they are same.
+	 */
+	if (!pid) {
+		mmget(current->mm);
+		*mem_nodes = cpuset_mems_allowed(current);
+		return current->mm;
+	}
 
 	/* Find the mm_struct */
 	rcu_read_lock();
-	task = pid ? find_task_by_vpid(pid) : current;
+	task = find_task_by_vpid(pid);
 	if (!task) {
 		rcu_read_unlock();
-		return -ESRCH;
+		return ERR_PTR(-ESRCH);
 	}
 	get_task_struct(task);
 
@@ -1900,22 +1894,47 @@ static int kernel_move_pages(pid_t pid,
 	 */
 	if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
 		rcu_read_unlock();
-		err = -EPERM;
+		mm = ERR_PTR(-EPERM);
 		goto out;
 	}
 	rcu_read_unlock();
 
- 	err = security_task_movememory(task);
- 	if (err)
+	mm = ERR_PTR(security_task_movememory(task));
+	if (IS_ERR(mm))
 		goto out;
-
-	task_nodes = cpuset_mems_allowed(task);
+	*mem_nodes = cpuset_mems_allowed(task);
 	mm = get_task_mm(task);
+out:
 	put_task_struct(task);
-
 	if (!mm)
+		mm = ERR_PTR(-EINVAL);
+	return mm;
+}
+
+/*
+ * Move a list of pages in the address space of the currently executing
+ * process.
+ */
+static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
+			     const void __user * __user *pages,
+			     const int __user *nodes,
+			     int __user *status, int flags)
+{
+	struct mm_struct *mm;
+	int err;
+	nodemask_t task_nodes;
+
+	/* Check flags */
+	if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
 		return -EINVAL;
 
+	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
+		return -EPERM;
+
+	mm = find_mm_struct(pid, &task_nodes);
+	if (IS_ERR(mm))
+		return PTR_ERR(mm);
+
 	if (nodes)
 		err = do_pages_move(mm, task_nodes, nr_pages, pages,
 				    nodes, status, flags);
@@ -1924,10 +1943,6 @@ static int kernel_move_pages(pid_t pid,
 
 	mmput(mm);
 	return err;
-
-out:
-	put_task_struct(task);
-	return err;
 }
 
 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
_

  parent reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-17 23:13 incoming Andrew Morton
2020-10-17 23:13 ` [patch 01/40] ia64: fix build error with !COREDUMP Andrew Morton
2020-10-17 23:13 ` [patch 02/40] mm, memcg: rework remote charging API to support nesting Andrew Morton
2020-10-17 23:13 ` [patch 03/40] mm: kmem: move memcg_kmem_bypass() calls to get_mem/obj_cgroup_from_current() Andrew Morton
2020-10-17 23:13 ` [patch 04/40] mm: kmem: remove redundant checks from get_obj_cgroup_from_current() Andrew Morton
2020-10-17 23:13 ` [patch 05/40] mm: kmem: prepare remote memcg charging infra for interrupt contexts Andrew Morton
2020-10-17 23:13 ` [patch 06/40] mm: kmem: enable kernel memcg accounting from " Andrew Morton
2020-10-17 23:13 ` [patch 07/40] mm/memory-failure: remove a wrapper for alloc_migration_target() Andrew Morton
2020-10-17 23:14 ` [patch 08/40] mm/memory_hotplug: " Andrew Morton
2020-10-17 23:14 ` Andrew Morton [this message]
2020-10-17 23:14 ` [patch 10/40] mm/mmap: add inline vma_next() for readability of mmap code Andrew Morton
2020-10-17 23:14 ` [patch 11/40] mm/mmap: add inline munmap_vma_range() for code readability Andrew Morton
2020-10-17 23:14 ` [patch 12/40] mm/gup_benchmark: take the mmap lock around GUP Andrew Morton
2020-10-17 23:14 ` [patch 13/40] binfmt_elf: take the mmap lock around find_extend_vma() Andrew Morton
2020-10-17 23:14 ` [patch 14/40] mm/gup: assert that the mmap lock is held in __get_user_pages() Andrew Morton
2020-10-17 23:14 ` [patch 15/40] mm/gup_benchmark: rename to mm/gup_test Andrew Morton
2020-10-17 23:14 ` [patch 16/40] selftests/vm: use a common gup_test.h Andrew Morton
2020-10-17 23:14 ` [patch 17/40] selftests/vm: rename run_vmtests --> run_vmtests.sh Andrew Morton
2020-10-17 23:14 ` [patch 18/40] selftests/vm: minor cleanup: Makefile and gup_test.c Andrew Morton
2020-10-17 23:14 ` [patch 19/40] selftests/vm: only some gup_test items are really benchmarks Andrew Morton
2020-10-17 23:14 ` [patch 20/40] selftests/vm: gup_test: introduce the dump_pages() sub-test Andrew Morton
2020-10-17 23:14 ` [patch 21/40] selftests/vm: run_vmtests.sh: update and clean up gup_test invocation Andrew Morton
2020-10-17 23:14 ` [patch 22/40] selftests/vm: hmm-tests: remove the libhugetlbfs dependency Andrew Morton
2020-10-17 23:14 ` [patch 23/40] selftests/vm: 10x speedup for hmm-tests Andrew Morton
2020-10-17 23:14 ` [patch 24/40] mm/madvise: pass mm to do_madvise Andrew Morton
2020-10-17 23:14 ` [patch 25/40] pid: move pidfd_get_pid() to pid.c Andrew Morton
2020-10-17 23:14 ` [patch 26/40] mm/madvise: introduce process_madvise() syscall: an external memory hinting API Andrew Morton
2020-10-17 23:15 ` [patch 27/40] mm: update the documentation for vfree Andrew Morton
2020-10-17 23:15 ` [patch 28/40] mm: add a VM_MAP_PUT_PAGES flag for vmap Andrew Morton
2020-10-17 23:15 ` [patch 29/40] mm: add a vmap_pfn function Andrew Morton
2020-10-17 23:15 ` [patch 30/40] mm: allow a NULL fn callback in apply_to_page_range Andrew Morton
2020-10-17 23:15 ` [patch 31/40] zsmalloc: switch from alloc_vm_area to get_vm_area Andrew Morton
2020-10-17 23:15 ` [patch 32/40] drm/i915: use vmap in shmem_pin_map Andrew Morton
2020-10-17 23:15 ` [patch 33/40] drm/i915: stop using kmap in i915_gem_object_map Andrew Morton
2020-10-17 23:15 ` [patch 34/40] drm/i915: use vmap " Andrew Morton
2020-10-17 23:15 ` [patch 35/40] xen/xenbus: use apply_to_page_range directly in xenbus_map_ring_pv Andrew Morton
2020-10-17 23:15 ` [patch 36/40] x86/xen: open code alloc_vm_area in arch_gnttab_valloc Andrew Morton
2020-10-17 23:15 ` [patch 37/40] mm: remove alloc_vm_area Andrew Morton
2020-10-17 23:15 ` [patch 38/40] mm: cleanup the gfp_mask handling in __vmalloc_area_node Andrew Morton
2020-10-17 23:15 ` [patch 39/40] mm: remove the filename in the top of file comment in vmalloc.c Andrew Morton
2020-10-17 23:15 ` [patch 40/40] mm: remove duplicate include statement in mmu.c Andrew Morton

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